Conventional recording-reproduction apparatus of the type mentioned wherein a magnetic tape is used include the one disclosed in Unexamined Japanese Patent Publications HEI 1-220164 and HEI 1-220165. The present invention provides an improvement over this conventional apparatus, so that the conventional apparatus will be described first briefly. In the following description, the direction in which the cassette is loaded into the apparatus will be referred to as the "front," and the direction of unloading of the cassette as the "rear."
With reference to FIGS. 33 to 38B, the apparatus has a rotary cylinder 800 and a pair of reel supports 200a, 200b which are mounted on a chassis 100. The reel support 200a on the supply side has a band 722 wound therearound. The band 722 has one end attached to the chassis 100 and another end attached to a tension lever 720 which is movable about a pivot 725 on the chassis 100. The tension lever 720 is biased counterclockwise by a spring 723 into pressing contact with a leading guide block 804 for withdrawing a magnetic tape from a cassette.
Disposed in the rear of the two reel supports 200a, 200b is a control slide 830 which is sliable rightward and leftward. A bell crank 831 in contact with a cam portion 830a of the control slide 830 causes a lever 832 to move the tension lever 720 with the sliding movement of the control slide 830. The slide 830 has a right end linked to a control plate 811 slidable forward and rearward on the chassis 100. The control plate 811 is connected to an intermediate plate 815 provided on the rear side of the chassis 100. A pin 812 extending upward from the intermediate plate 815 is fitted in a cam groove 444 of a first cam gear 440 provided at a front end portion of the chassis 100 on the rear side thereof.
The reel supports 200a, 200b mesh respectively with intermediate gears 221, 222, and brake levers 241a, 241b bear on these gears 221, 222, respectively. A spring 255 causes the brake levers 241a, 241b to give a braking load to the intermediate gears 221, 222.
One end of a slide piece 932 positioned between the control slide 830 and the upper surface of the chassis 100 is opposed to one of the brake levers, 241b. The slide piece 932 is perpendicular to and engaged with an intermediate slide 931 interposed between the chassis 100 and the control plate 811. The slide 931 is in contact with an intermediate lever 930, which in turn is in contact with a clutch unit 340 slidable rightward and leftward on the chassis 100. The clutch unit 340 is disposed on the front side of the chassis 100 opposite to the first cam gear 440. Disposed in front of the clutch unit 340 is a pulley 518 which is rotatable by a motor 515 by means of a belt. The rotation of the pulley 518 is transmitted to the first cam gear 440 by a mechanism which will not be described.
The first cam gear 440 is in mesh with a second cam gear 810 having a cam groove 813a, in which one end of a rack bar 321 is engaged. The rack bar 321 is in mesh with a drive gear 320b coupled to a leading guide block 804 at right by a link mechanism 428. Similarly, the leading guide block 804 at left has a link mechanism 428 connected thereto and a drive gear 320a coupled thereto.
With reference to FIG. 37A showing the clutch unit 340, a slide plate 341 has mounted thereon a clutch lever 349 rotatable along a plane perpendicular to the chassis 100, and a pin 346 which is slidable upward and downward. The pin 346 extends through the chassis 100 and is fitted in a vertical cam groove (not shown) in the first cam gear 440. The clutch unit 340 is biased leftward by a spring 142. In EJECT mode, the unit 340 is in pressing contact with a stopper 141 on the chassis 100, and a pawl 348 at the free end of the clutch lever 349 is positioned at the left of a projecting shaft 517 of the pulley 518.
When a cassette is loaded into the apparatus, the apparatus is first set in STOP mode as shown in FIG. 35. The cam gears 440, 810 rotate in operative relation with the motor 515, and the rack bar 321 slides obliquely rightward to rotate the drive gear 320b in a tape withdrawing direction. The leading guide blocks 804, 804 withdraw a magnetic tape 601 and press the tape against catchers 806 provided in front of the rotary cylinder 800.
With the rotation of the motor 515, the pulley 518 rotates clockwise, causing the intermediate plate 815 and the control plate 811 to slidingly move the control slide 830 leftward. The bell crank 831 in engagement with the cam portion 830a causes the lever 832 to bear against a base end portion of the tension ever 720 to restrain the rotation of the lever 720 by the spring 723 and slacken the bank 722. A guide pin 721 provided upright on the forward end of the tension lever 720 reaches a position a small distance away from the magnetic tape 601.
When STOP mode is changed over to FF/REW mode in which the magnetic tape 601 is forwarded fast or rewound, the first cam gear 440 causes the pin 346 to push the clutch unit 340 rightward against the spring 142. The clutch unit 340 pushes the slide piece 932 leftward through the intermediate lever 930 and the intermediate slide 931. With reference to FIG. 37B, the pin 346 is forced upward as the pin slides along the vertical cam groove, rotating the clutch lever 349 counterclockwise about its pivot. Upon the pawl 348 reaching the right side of the projecting shaft 517, the pin 346 is released from the cam groove and descends, and the clutch unit 340 is forced leftward by the spring to engage the pawl 348 with the shaft 517 as shown in FIG. 38A.
With reference to FIG. 36, the brake lever 241b rotates about its pivot by being pushed by the slide piece 932 and kicks up the other brake lever 241a, with the result that the two levers 241a, 241b are moved away from the intermediate gears 221, 222. The tension lever 720 is in the same position as in STOP mode.
When FF/REW mode is changed over to STOP mode, the pulley 518 rotates counterclockwise with the rotation of the motor 515. Owing to the friction between the shaft 517 and the pawl 348, the clutch lever 349 rotates upward about its pivot, releasing the pawl 348 from the shaft 517 (see FIG. 37B), whereupon the clutch unit 340 is returned by the spring 142.
The clutch unit 340 releases the intermediate lever 930 from contact therewith, permitting the spring 255 on the brake levers 241a, 241b to return the slide piece 932 and the intermediate slide 93l to their stand-by position. Instantaneously the brake levers 241a, 241b come into contact with the respective intermediate gears 221, 222, thus exerting a braking force on the reel supports 200a, 200b instantaneously upon a change-over from FF/REW mode to STOP mode. The braking force thus instantaneously given prevents the reel support 200b from being rotated by inertia in STOP mode and the magnetic tape 601 from slackening.
When STOP mode is changed over to PLAY mode for the reproduction of record, the control slide 830 slidingly moves leftward, releasing the bell crank 831 from engagement with the control slide 830 and permitting the tension lever 720 to rotate counterclockwise to tension the band 722, whereby a predetermined load of rotation is given to the take-up reel support 200b. This imparts suitable tension to the magnetic tape 601 to enable the tape 601 to travel smoothly. As seen in FIG. 38B, the clutch unit 340 further slides rightward to move the pawl 348 away from the projecting shaft 517.
However, the recording-reproduction apparatus has the following problems.
1. Since the single pin 812 engaging with the first cam gear 440 slidingly moves the control plate 811, an attempt-to increase the length of sliding stroke of the control plate 811 and the control slide 830 requires an increase in the size of the first cam gear 440. Because the control slide 830 is made movable rightward and leftward on the chassis 100, the increase in the stroke length of the plate 811 and the slide 830 results in an increase in the size of the chassis 100, consequently presenting difficulty in fulfilling the requirement in recent years that recording-reproduction apparatus be made smaller. PA1 2. The meshing engagement of the drive gear 320b with the rack bar 321 invariably involves a backlash resulting from the machining process as is well known. The leading guide block 804 is biased forward by the tension lever 720 and is therefore pushed forward by an amount corresponding to the backlash in EJECT mode. If the backlash is great owing to variations in the accuracy of machining drive gears 320a, it is likely that the magnetic tape 601 will be damaged by being caught by the guide block 804 when the cassette is loaded onto the chassis 100. PA1 3. For the toothed periphery of the drive gear 320a to withstand a great force exerted thereon when the guide block 804 is pressed against the catcher 806 for tape loading, the gear needs to have an increased module. However, the increased module causes the rack bar 321 to backlash greatly to displace the guide block 804 forward, giving rise to the same problem as above. PA1 4. The powder of the first cam gear 440 is transmitted to the tension lever 720 by way of the control plate 811, control slide 830, bell crank 831 and lever 832, so that the tension lever 720 is slow in responding to the rotation of the first cam gear 440. This presents difficulty in effecting delicate control of operation timing. PA1 5. In EJECT mode, the spring 723 is tensioned to the greatest extent by the tension lever 720, so that the control slide 830 is subjected to a greater load than in PLAY mode and encounters difficulty in sliding smoothly. PA1 6. When the brake lever 241b is instantaneously brought into contact with the intermediate gear 222 in engagement with the reel support 200b upon a change-over from FF/REW mode to STOP mode, the clutch unit 340 instantaneously moves leftward into striking contact with the stopper 141. Accordingly, the resilient restoring force of the spring 142 acts directly on the stopper 141, so that the impact noise produced by the collision of the clutch unit 340 therewith is great, has a high frequency and sounds disagreeable. The impact noise may be mitigated by covering the stopper 141 with a rubber or like shock absorber, whereas this adds to the number of components.